package org.helium.util;

import java.io.ByteArrayOutputStream;
import java.io.DataOutputStream;
import java.io.IOException;

/**
 * @author coral
 * @version 创建时间：2015年4月22日
 * 类说明
 */
public class Base64 {
	private static final String Base64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

	private Base64() {
	}

	/**
	 * Convert binary data to a base64-encoded String
	 * 
	 * @param b
	 *            An array containing binary data
	 * @return A String containing the encoded data
	 */
	public static String toString(byte[] b) {
		ByteArrayOutputStream os = new ByteArrayOutputStream();

		for (int i = 0; i < (b.length + 2) / 3; i++) {
			short[] s = new short[3];
			short[] t = new short[4];
			for (int j = 0; j < 3; j++) {
				if ((i * 3 + j) < b.length)
					s[j] = (short) (b[i * 3 + j] & 0xFF);
				else
					s[j] = -1;
			}

			t[0] = (short) (s[0] >> 2);
			if (s[1] == -1)
				t[1] = (short) (((s[0] & 0x3) << 4));
			else
				t[1] = (short) (((s[0] & 0x3) << 4) + (s[1] >> 4));
			if (s[1] == -1)
				t[2] = t[3] = 64;
			else if (s[2] == -1) {
				t[2] = (short) (((s[1] & 0xF) << 2));
				t[3] = 64;
			} else {
				t[2] = (short) (((s[1] & 0xF) << 2) + (s[2] >> 6));
				t[3] = (short) (s[2] & 0x3F);
			}
			for (int j = 0; j < 4; j++)
				os.write(Base64.charAt(t[j]));
		}
		return new String(os.toByteArray());
	}

	/**
	 * Formats data into a nicely formatted base64 encoded String
	 * 
	 * @param b
	 *            An array containing binary data
	 * @param lineLength
	 *            The number of characters per line
	 * @param prefix
	 *            A string prefixing the characters on each line
	 * @param addClose
	 *            Whether to add a close parenthesis or not
	 * @return A String representing the formatted output
	 */
	public static String formatString(byte[] b, int lineLength, String prefix, boolean addClose) {
		String s = toString(b);
		StringBuffer sb = new StringBuffer();
		for (int i = 0; i < s.length(); i += lineLength) {
			sb.append(prefix);
			if (i + lineLength >= s.length()) {
				sb.append(s.substring(i));
				if (addClose)
					sb.append(" )");
			} else {
				sb.append(s.substring(i, i + lineLength));
				sb.append("\n");
			}
		}
		return sb.toString();
	}

	/**
	 * Convert a base64-encoded String to binary data
	 * 
	 * @param str
	 *            A String containing the encoded data
	 * @return An array containing the binary data, or null if the string is
	 *         invalid
	 */
	public static byte[] fromString(String str) {
		ByteArrayOutputStream bs = new ByteArrayOutputStream();
		byte[] raw = str.getBytes();
		for (int i = 0; i < raw.length; i++) {
			if (!Character.isWhitespace((char) raw[i]))
				bs.write(raw[i]);
		}
		byte[] in = bs.toByteArray();
		if (in.length % 4 != 0) {
			return null;
		}

		bs.reset();
		DataOutputStream ds = new DataOutputStream(bs);

		for (int i = 0; i < (in.length + 3) / 4; i++) {
			short[] s = new short[4];
			short[] t = new short[3];

			for (int j = 0; j < 4; j++)
				s[j] = (short) Base64.indexOf(in[i * 4 + j]);

			t[0] = (short) ((s[0] << 2) + (s[1] >> 4));
			if (s[2] == 64) {
				t[1] = t[2] = (short) (-1);
				if ((s[1] & 0xF) != 0)
					return null;
			} else if (s[3] == 64) {
				t[1] = (short) (((s[1] << 4) + (s[2] >> 2)) & 0xFF);
				t[2] = (short) (-1);
				if ((s[2] & 0x3) != 0)
					return null;
			} else {
				t[1] = (short) (((s[1] << 4) + (s[2] >> 2)) & 0xFF);
				t[2] = (short) (((s[2] << 6) + s[3]) & 0xFF);
			}

			try {
				for (int j = 0; j < 3; j++)
					if (t[j] >= 0)
						ds.writeByte(t[j]);
			} catch (IOException e) {
			}
		}
		return bs.toByteArray();
	}
}
